CN113929326A

CN113929326A - Preparation method and preparation system of cement

Info

Publication number: CN113929326A
Application number: CN202111414853.6A
Authority: CN
Inventors: 梁晓杰; 常景彩; 王勇; 王鹏; 李蜀生; 马春元
Original assignee: Qingdao Haitai Energy Science And Technology Research Institute; Shandong University
Current assignee: Qingdao Haitai Energy Science And Technology Research Institute; Shandong University
Priority date: 2021-11-25
Filing date: 2021-11-25
Publication date: 2022-01-14
Anticipated expiration: 2041-11-25
Also published as: CN113929326B

Abstract

The invention discloses a preparation method and a preparation system of cement, which are characterized in that after raw materials of the cement are uniformly mixed according to a ratio, CO-rich is intermittently introduced into mixed powder in the processes of grinding and selecting the mixed powder₂And gas, wherein the carbonation degree of the cement is controlled to be 0.05-1%. Introducing CO-rich gas into the cement production link₂The smoke gas controls the cement to be in a weak carbonation degree, and the weak carbonation cement and the non-carbonated cement are mixed by utilizing an intermittent control method, so that the interaction of weak carbonation and hydration is exerted, the basic calcium carbonate is promoted to be generated in the early stage of cement hydration, and the generated basic calcium carbonate can promote the interface area of cement particles to become compact, thereby enhancing the comprehensive performance of the cement.

Description

Preparation method and preparation system of cement

Technical Field

The invention belongs to the technical field of cement preparation, and particularly relates to a preparation method and a preparation system of cement.

Background

The statements herein merely provide background information related to the present disclosure and may not necessarily constitute prior art.

China has large cement yield, and a large amount of CO can be discharged in the cement production process₂The emission reduction pressure in the cement industry is severe. Four major minerals C in cement clinker₃S、C₂S、C₃A and C₄AF in the presence of water and a concentration of CO₂Under the condition of (2), the catalyst is easy to react with CO₂A carbonation reaction occurs, but these four minerals also play a decisive role in the cement performance during the hydration of the cement. The inventors have found that if the four minerals are carbonated to too great a degree, CaCO is formed on the surface of the cement particles₃The shell layer structure of (2) can prevent hydration of cement and reduce strength of cement.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a preparation method and a preparation system of cement. Introducing CO-rich gas into the cement production link₂The smoke controls the carbonation degree of the cement in a weak state in an intermittent manner by regulating and controlling technological parameters, balances the interaction relation between intermittent weak carbonation treatment and hydration, and plays a two-way role in reducing carbon and improving performance in cement production by utilizing the carbonation and hydration interaction mechanism.

In order to achieve the purpose, the invention is realized by the following technical scheme:

in the first aspect, the invention provides a method for preparing cement, which comprises the steps of uniformly mixing raw materials of the cement according to a ratio, and intermittently introducing CO-rich into mixed powder in the processes of grinding and selecting the mixed powder₂Gas, controlling the carbonation degree of the cement to be less than or equal to 1 percent.

Carbonation level (mass after carbonation-mass before carbonation)/mass before carbonation.

In a second aspect, the invention provides a cement preparation system, which comprises a cement powder production system and an air distribution system, wherein the cement powder production system comprises a grinding device and a powder selecting device, an air distribution system inlet and a CO-rich system₂The gas source is connected, and the outlet is communicated with the grinding device and the powder selecting device.

The above-described one or more embodiments of the present invention achieve the following advantageous effects:

the key core points of the invention are as follows: (1) intermittent carbonation; (2) the weak carbonation degree is controlled to be less than or equal to 1 percent, mainly because the carbonation and hydration effects are embodied in the inhibition and promotion effects, the inhibition effect is that the active minerals of the cement are consumed by carbonation, and the carbonation product generated on the surface hinders the hydration of the cement; the promoting effect is shown in the following parts: CaCO produced by carbonation₃As a "nucleus", C in cement can be promoted₃S participates in the hydration reaction of cement to improve the interface strength, so that the intermittent weak carbonation control system is adopted to mix weak carbonated cement and non-carbonated cement to play the interaction of weak carbonation and hydration to promote the early generation of basic calcium carbonate during the hydration of the cement.

Introducing CO-rich gas into the cement production link₂The smoke gas controls the cement to be in a weak carbonation degree, and the weak carbonation cement and the non-carbonated cement are mixed by utilizing an intermittent control method, so that the interaction of weak carbonation and hydration is exerted, the basic calcium carbonate is promoted to be generated in the early stage of cement hydration, and the generated basic calcium carbonate can promote the interface area of cement particles to become compact, thereby enhancing the comprehensive performance of the cement.

The carbonation technology is applied to the cement production, thereby not only reducing CO₂The discharge of the cement and the comprehensive performance of the cement are improved.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.

FIG. 1 is a CaCO formed by carbonated cement at 6.5% carbonation level₃A shell layer structure micro-topography picture, wherein a and b are scanning electron micrographs with different magnification ratios, and c is an energy spectrum at a point 1 in the b picture;

FIG. 2 is a scanning electron micrograph at different magnifications of the micro-topography formed by weakly carbonated cement at a carbonation level of 0.13%;

FIG. 3 is a comparison of the micro-topography of a 3-day hardened slurry of uncarbonated cement (a) and batch carbonated cement (b);

FIG. 4 is a scanning electron microscope (a) of the micro-morphology of basic calcium carbonate generated in 3-day hardening slurry of intermittent weakly carbonated cement, and energy spectrum diagrams corresponding to 1 point, 2 points and 3 points in the scanning electron microscope (a) are respectively a diagram (b), (c) and (d);

FIG. 5 is a process flow diagram in example 1.

In the figure: the mutual spacing or size is exaggerated to show the position of each part, and the schematic diagram is only used for illustration;

the device comprises a material conveying device 1, a first bucket type elevator 2, a V-shaped powder concentrator 3, a middle bin 4, a roller press 5, a roller press 6, a first finished product powder concentrator 7, a cyclone dust collector 8, a circulating fan 9, a ball mill 10, a second bucket type elevator 11, a second finished product powder concentrator 12, a tail grinding dust collecting system 13, a main dust collector 14, a main exhaust fan 15 and a finished product warehousing system.

Detailed Description

It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

In the prior art, researches related to the use of materials such as steel slag subjected to carbonation treatment for producing materials such as concrete have been carried out, but when the carbonation technology is directly applied to the preparation of cement, the inventor finds that the comprehensive performance of the cement is difficult to be obviously improved, and even the comprehensive performance of the cement is adversely affected. The carbonation process of the cement manufacturing process has thus been studied extensively.

It was found that when the degree of carbonation of cement was 6.5% (degree of carbonation ═ mass after carbonation-mass before carbonation)/mass before carbonation), CaCO was formed on the surface of cement particles₃As shown in fig. 1, the shell structure can block hydration of cement and reduce the strength of the cement; when the carbonation degree of the cement is 0.13%, a weak carbonation reaction is generated on the surface of the cement particles as shown in FIG. 2, in which CaCO is generated during the carbonation of the cement₃The small size of the crystal particles is easy to participate in the process of cement hydration, so that the relationship between the carbonation treatment of the cement and the cement hydration has the inhibiting and promoting effects.

Based on the above findings, the inventors have continued intensive research and found a method which can play a role in reducing carbon and improving the performance of cement production.

In order to achieve the purpose, the invention provides a preparation method of cement, which comprises the steps of uniformly mixing raw materials of the cement according to a ratio, and intermittently introducing CO-rich gas into mixed powder in the processes of grinding and selecting the mixed powder₂Gas, controlling the carbonation degree of the cement to be less than or equal to 1 percent.

In some embodiments, the CO-rich feed is intermittent₂The method of the gas comprises the following steps: after the continuous feeding is carried out for 20-60min, the feeding is suspended for 10-30min, and the feeding is circulated according to the mode.

In some embodiments, the carbonation level of the cement is controlled to be between 0.05% and 1%.

In some embodiments, the cement raw material is selected from clinker, limestone, natural gypsum, desulfurized gypsum, citric acid residue, coal gangue, fly ash, slag powder, steel slag powder, grinding aid.

In some embodiments, the total moisture of the mixed meal is less than or equal to 1% during grinding.

In some embodiments, the CO is enriched₂The gas being rich in CO₂Flue gas.

Further, rich in CO₂In flue gas, CO₂Content > 20%, H₂The content of O is less than or equal to 10 percent, and the temperature of the flue gas is less than or equal to 130 ℃. The gypsum is prevented from removing crystal water at high temperature, and cement false coagulation is avoided.

Further, rich in CO₂In flue gas, CO₂20% -60% of H₂The content of O is 1-10%, and the temperature of the flue gas is 30-130 ℃.

In some embodiments, the temperature of the cement is 130 ℃ or less during the grinding process.

In some embodiments, the milling is ball milling, roller milling, or roller and mill combined milling.

In some embodiments, the cement powder production system comprises a primary grinding system and a secondary grinding system connected in series; a V-shaped powder concentrator is arranged in the first-stage grinding system, a ball mill is arranged in the second-stage grinding system, and the ball mill is connected with an outlet of the V-shaped powder concentrator;

the air distribution system is communicated with the V-shaped powder concentrator and the ball mill.

Furthermore, one-level milling system includes first lifting machine, V type selection powder machine and the roller press of end to end connection in proper order, and the large granule material export and the roller press access connection of V type selection powder machine.

Furthermore, the fine particle material outlet of the V-shaped powder concentrator is connected with the ball mill through the first finished product powder concentrator.

Further, second grade milling system includes second lifting machine, second finished product selection powder machine and the ball mill of end to end connection in proper order, and the large granule material export of second finished product selection powder machine is connected with the ball mill, and second finished product selection powder machine and air distribution system intercommunication.

Furthermore, the fine particle material separator further comprises a main dust collector, wherein a fine particle material outlet of the second finished product powder concentrator is connected with the main dust collector, and the main dust collector is connected with a main exhaust fan.

It should be noted thatThe influence of weather, in rainy, winter or other humid climates, in which the water content in the air rises, is suitably reduced by introducing CO in an amount sufficient to reduce the amount of CO₂The adjustment range of the total amount of the flue gas is 1-10%, because the moisture content in the grinding system is increased in a humid climate, the carbonation rate and the carbonation degree are increased, and the carbonation degree of the cement needs to be reduced. According to the above-mentioned technological operation method, the cement is undergone the process of intermittent weak carbonation pretreatment. The homogenization process of 'weak carbonation treated cement + non-carbonation treated cement' is achieved through the homogenization of the chute delivery and the Roots blower in the finished product warehouse.

The invention is further illustrated by the following figures and examples.

The cement ball mill grinding process is explained as an example.

The raw materials used in the cement production process comprise 50-80% of clinker, 2-5% of limestone, 2-5% of natural gypsum, 2-5% of desulfurized gypsum, 1-2% of coal gangue, 3-8% of fly ash, 5-15% of slag powder, 3-5% of steel slag powder, 0.3-2% of additives such as grinding aids and the like, wherein the water content of the clinker, the slag powder, the fly ash and the steel slag powder is generally less than 1%, the water content of the natural gypsum, the limestone and the coal gangue is generally less than 5%, the water content of the desulfurized gypsum is generally less than 20%, the water content of the grinding aids is generally more than 90%, and the total water content of the materials entering the cement grinding equipment is controlled to be less than or equal to 1% by controlling the proportion adjustment and the water content control measures (such as airing, drying and the like) of the raw materials.

The specific process comprises the following steps:

(1) after being measured by a weighing scale, the raw materials are gathered and enter a material conveying device 1, a moisture detector is arranged on the upper portion of the conveying device and used for detecting the whole moisture of the materials, the sum of the moisture of all the materials is required to be less than or equal to 1% for control, and then the raw materials enter a first bucket elevator 2.

(2) After being lifted to a certain height by the bucket elevator 2, the materials fall into the V-shaped powder concentrator 3 to be scattered, particles with smaller particle sizes in the materials are brought into the finished product powder concentrator 6 by airflow and air pressure provided by the circulating fan 8, and qualified finished products are collected by the cyclone dust collector 7 and enter the finished product warehousing system 15. The material with unqualified granularity enters the intermediate bin 4 from the lower part of the V-shaped powder concentrator 3 and enters the inlet 9 of the ball mill from the lower part of the finished product powder concentrator 6.

(3) And (3) feeding the material in the intermediate bin 4 into a roller press 5, extruding and crushing large particles in the material, and repeating the above circulation to select the material with fine particle size. The above circulation control is performed by the air flow and the air pressure supplied from the circulation fan 8.

(4) The material entering the inlet of the ball mill 9 from the lower part of the first finished product powder selecting machine 6 is ground by the ball mill, enters a second bucket elevator 10, is lifted to a certain height and enters a second finished product powder selecting machine 11, and the product with qualified granularity is selected and enters a main dust collector 13 and a finished product warehousing system 15; and the material with unqualified granularity enters the inlet of the ball mill 9 from the lower part of the second finished product powder selecting machine 11. The above material circulation control is performed by the air flow and the air pressure provided by the tail grinding dust collecting system 12 and the main exhaust fan 14.

(5) Three-way valves and CO which can be automatically controlled are respectively arranged at the tertiary air inlets of the first finished product powder selecting machine 6 and the second finished product powder selecting machine 11 and the inlet of the ball mill 9₂Concentration detector and gas flow moisture detector based on CO₂The concentration, the moisture of the airflow and the moisture of the material are adjusted, the intermittent time of weak carbonation is adjusted, and the material is rich in CO₂The flue gas is introduced from the three-way valve, and the action time of the three-way valve is set according to the set intermittent time of weak carbonation.

Require control of CO enrichment₂The control indexes of the flue gas are as follows: CO 2₂Content > 20%, H₂The content of O is less than or equal to 10 percent, the temperature of flue gas is less than or equal to 130 ℃, and the problem of cement false set caused by crystal water removal of gypsum at high temperature is avoided. The temperature of the cement is controlled to be less than or equal to 130 ℃ in the grinding process. Controlling CO enrichment₂The amount of the flue gas accounts for 20-80% of the gas flow, the introduction of the flue gas is controlled intermittently, and CO-rich gas is continuously introduced₂The time of the flue gas is controlled to be 20-60min, and the introduction of CO-rich gas is stopped at intervals of 10-30min₂Flue gas, introducing oxygen in such a way that the oxygen is circulated, and operating in accordance with the control of waterThe carbonation degree of the mud is 0.05 to 1 percent.

The flexural strength and the compressive strength of the cement subjected to the intermittent weak carbonation treatment and the cement not subjected to the intermittent weak carbonation treatment are measured, the improvement ratio of the flexural strength and the compressive strength is more than 10 percent, and the detection data are shown in table 1:

TABLE 1

Example 1

The cement ball mill grinding process is explained as an example.

The raw materials used in the cement production process comprise 60% of clinker, 4% of limestone, 3% of natural gypsum, 5% of desulfurized gypsum, 2% of coal gangue, 5% of fly ash, 10% of slag powder, 5% of steel slag powder, 1% of grinding aid and other additives, and the total moisture of the materials entering the cement grinding equipment is controlled to be less than or equal to 1% by controlling the proportion adjustment of the raw materials and the moisture control measures (such as airing, drying and the like).

The specific process is the same as the above process.

Require control of CO enrichment₂The control indexes of the flue gas are as follows: CO 2₂20% -25%, H₂The content of O is 7-10 percent, the temperature of the flue gas is 120-. The temperature of the cement is controlled to be 130 ℃ in the grinding process. Controlling CO enrichment₂The smoke amount accounts for 60 percent of the gas flow (rich in CO)₂60 percent of flue gas and 40 percent of air) is introduced according to the intermittent control, and CO-rich gas is continuously introduced₂The time of the flue gas is controlled at 30min, and the introduction of CO-rich gas is stopped at intervals of 20min₂And (3) circularly introducing oxygen into the flue gas in the mode, wherein the operation is based on the principle of controlling the carbonation degree of the cement to be 1%.

The flexural strength and compressive strength of the cement subjected to the batch type weak carbonation treatment and the cement not subjected to the batch type weak carbonation treatment were measured, and the detection data are shown in table 2:

TABLE 2

By analyzing hydration heat curves of the cement subjected to the intermittent weak carbonation treatment and the cement not subjected to the intermittent weak carbonation treatment and electron micrographs and microstructure of hydration products, the first exothermic peak in the early stage of hydration induction of the cement subjected to the intermittent weak carbonation treatment is 20 minutes earlier than that of the cement not subjected to the intermittent weak carbonation treatment, and meanwhile, the accumulated exothermic total amount is larger.

By enriching with CO₂The flue gas of the clinker rotary kiln, the lime rotary kiln or other production processes is introduced into the production flow of the cement by adjusting the water content in the cement, the amount of the introduced flue gas and the CO of the introduced flue gas₂The concentration, the moisture content in the flue gas, the mode and the time of the interval of introducing the flue gas and the like, the intermittent weak carbonation pretreatment is carried out in the cement generation process, and the generated cement product comprises the mixture of cement which is not subjected to the weak carbonation treatment and cement which is subjected to the weak carbonation treatment, namely the mixture of the cement which is subjected to the partial weak carbonation treatment and the cement which is not subjected to the weak carbonation treatment is mixed, wherein the proportion of the weak carbonation cement is determined by the interval of introducing the flue gas, the content of the flue gas and the CO in the flue gas₂The concentration of (a), the moisture in the flue gas, etc. By carrying out intermittent weak carbonation treatment in the cement production process, the interaction of weak carbonation and hydration is formed between the cement and uncarbonated cement, and basic calcium carbonate (Ca) is formed at the early stage of cement hydration₃(OH)₂(CO₃)₂·1.5H₂O) (see FIG. 2) the basic calcium carbonate can reinforce the interfacial strength (see FIGS. 3 and 4) of the transition zone between cement particles, and thus, can function to absorb CO₂And the comprehensive performance of the cement is enhanced.

By comparing and analyzing the micro-morphology and energy spectrum of the uncarbonated cement and the intermittent weak-carbonated cement 3d hydration products (see fig. 3 and 4), the obvious interaction between the intermittent weak carbonation and the hydration can be known, the 3-day hardened slurry has compact structure, few pores among the cement particles and fuzzy boundary, and the cement particles are tightly connected through the hydration products. In fig. 4, the percentage of each element in the b, c, and d graphs is shown in table 3.

TABLE 3

Element(s)	1 point atomic percent/%)	2 point atomic percent/%)	3 point atomic percent/%)
				C	14.18	19.13	23.6
O	62	67.14	51.01
				Ca	23.82	13.74	22.8
Mg	/	/	1.15
				Al	/	/	0.45
Si	/	/	0.99

Meanwhile, crystal particles with the size of about 500nm are found in the batch type weak carbonation cement 3d hardening slurry, and the Ca/C of the crystal particles is 23.82/14.18 and is approximately equal to 1.68 which is calculated by element analysis and atomic percent in EDS energy spectrum and conforms to basic calcium carbonate (Ca is the basic calcium carbonate)₃(OH)₂(CO₃)₂·1.5H₂O) Ca/C of 1.5, where the difference in Ca/C ratio may be in the bound CaCO₃The contents were different. The micro-morphology of the basic calcium carbonate is observed for the first time in the 3d hydration period.

23.77 million tons of cement are produced in 2020, the weak carbonation degree of cement is estimated to be 1%, and the carbon content per year is 23.77X 10 when about 50% of cement is subjected to weak carbonation treatment in the production process⁴X 0.3% × 50% ═ 1188.5 ten thousand tons.

The cement subjected to intermittent weak carbonation treatment has the advantages that the 3d breaking strength is improved by 0.5MPa, the 3d compressive strength is improved by about 1MPa, the addition amount of clinker in the cement can be saved by about 0.7%, the clinker price is about 400 yuan/ton, other mixed materials with the price of about 100 yuan/ton can be used for substitution, the cost of raw materials per ton of cement can be reduced by 0.7% × (400 yuan/100) ═ 2.1 yuan/ton, and the annual benefit created according to 23.77 million tons of cement is 23.77 × 2.1 ═ 49.92 million yuan.

Example 2

The specific process is the same as the above process.

Require control of CO enrichment₂The control indexes of the flue gas are as follows: CO 2₂40% -45% of H₂The content of O is 3-4 percent, the temperature of flue gas is 50-55 ℃, and the problem of cement false coagulation caused by crystal water removal of gypsum at high temperature is avoided. The temperature of the cement is controlled to be 100-110 ℃ in the grinding process. Controlling CO enrichment₂The smoke amount accounts for about 50% of the gas flow (rich in CO)₂50 percent of flue gas and 50 percent of air) is introduced according to the intermittent control, and CO-rich gas is continuously introduced₂The time of the flue gas is controlled at 30min, and the introduction of CO-rich gas is stopped at intervals of 10min₂The flue gas is circularly introduced with oxygen according to the mode, and the operation is based on the principle of controlling the carbonation degree of the cement to be 0.3 percent.

The flexural strength and compressive strength of the cement subjected to the batch type weak carbonation treatment and the cement not subjected to the batch type weak carbonation treatment were measured, and the detection data are shown in table 4:

TABLE 4

23.77 million tons of cement are produced in 2020, the weak carbonation degree of cement is estimated to be 0.3%, and the annual carbon fixation amount is 23.77X 10 when about 50% of cement is subjected to weak carbonation treatment in the production process⁴X 0.3% × 50% ═ 356.55 ten thousand tons.

The cement subjected to intermittent weak carbonation treatment has the advantages that the 3d breaking strength is improved by 1.5MPa, the 3d compressive strength is improved by about 3MPa, the addition amount of clinker in the cement can be saved by about 1.5%, the clinker price is about 400 yuan/ton, other mixed materials with the price of about 100 yuan/ton can be used for substitution, the cost of raw materials per ton of cement can be reduced by 1.5% × (400 yuan 100) ═ 4.5 yuan/ton, and the annual benefit created according to 23.77 million tons of cement is 23.77 × 4.5 ═ 106.97 million yuan.

Example 3

The specific process is as described above.

Require control of CO enrichment₂The control indexes of the flue gas are as follows: CO 2₂Content 21% -25%, H₂The content of O is 7-8%, the temperature of flue gas is about 105 ℃, and therefore the problem of cement false coagulation caused by crystal water removal of gypsum at high temperature is avoided. The temperature of the cement is controlled to be about 110 ℃ in the grinding process. Controlling CO enrichment₂The smoke amount accounts for about 40 percent of the gas flow (rich in CO)₂40 percent of flue gas and 60 percent of air) is introduced according to the intermittent control, and the CO-rich gas is continuously introduced₂The time of the flue gas is controlled at 40min, and the introduction of CO-rich gas is stopped at intervals of 30min₂And (3) circularly introducing oxygen into the flue gas in the mode, wherein the operation is based on the principle of controlling the carbonation degree of the cement to be 0.05%.

The flexural strength and the compressive strength of the cement subjected to the intermittent weak carbonation treatment and the cement not subjected to the intermittent weak carbonation treatment are measured, the improvement ratio of the flexural strength and the compressive strength is more than 10 percent, and the detection data are shown in table 5:

TABLE 5

23.77 million tons of cement are produced in 2020, the weak carbonation degree of cement is estimated to be 0.05%, and the carbon content per year is 23.77X 10 when about 50% of cement is subjected to weak carbonation treatment in the production process⁴X 0.05% × 50% ═ 59.425 ten thousand tons.

The cement subjected to intermittent weak carbonation treatment has the advantages that the 3d breaking strength is improved by 0.7MPa, the 3d compressive strength is improved by about 1.5MPa, the addition amount of clinker in the cement can be saved by about 1%, the clinker price is about 400 yuan/ton, other mixed materials with the price of about 100 yuan/ton can be used for replacing the clinker, the cost of raw materials per ton of cement can be reduced by 1.5% × (400 yuan/100) ═ 4.5 yuan/ton, and the annual benefit created according to 23.77 million tons of cement is 23.77 × 4.5 ═ 106.97 million yuan.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A preparation method of cement is characterized in that: after cement raw materials are uniformly mixed according to a ratio, CO-rich is intermittently introduced into the mixed powder in the processes of grinding and selecting the mixed powder₂Gas, controlling the carbonation degree of the cement to be less than or equal to 1 percent.

2. The method for producing cement according to claim 1, characterized in that: intermittent CO-rich introduction₂The method of the gas comprises the following steps: after the continuous feeding is carried out for 20-60min, the feeding is suspended for 10-30min, and the feeding is circulated according to the mode.

3. The method for producing cement according to claim 1, characterized in that: controlling the carbonation degree of the cement to be 0.05-1%.

4. The method for producing cement according to claim 1, characterized in that: the cement raw materials are selected from clinker, limestone, natural gypsum, desulfurized gypsum, citric acid residue, coal gangue, fly ash, slag powder, steel slag powder and grinding aid.

5. The method for producing cement according to claim 1, characterized in that: the total water content of the mixed powder is less than or equal to 1 percent during grinding.

6. According to claim1 the preparation method of the cement is characterized by comprising the following steps: rich in CO₂The gas being rich in CO₂Flue gas;

further, rich in CO₂In flue gas, CO₂Content > 20%, H₂The content of O is less than or equal to 10 percent, and the temperature of the flue gas is less than or equal to 130 ℃;

7. The method for producing cement according to claim 1, characterized in that: in the grinding process, the temperature of cement is less than or equal to 130 ℃;

8. A cement preparation system is characterized in that: comprises a cement powder production system and an air distribution system, wherein the cement powder production system comprises a grinding device and a powder selection device, the air distribution system is provided with an inlet and is rich in CO₂The gas source is connected, and the outlet is communicated with the grinding device and the powder selecting device.

9. The system for producing cement according to claim 8, wherein: the cement powder production system comprises a first-stage grinding system and a second-stage grinding system which are sequentially connected; a V-shaped powder concentrator is arranged in the first-stage grinding system, a ball mill is arranged in the second-stage grinding system, and the ball mill is connected with an outlet of the V-shaped powder concentrator;

the air distribution system is communicated with the V-shaped powder concentrator and the ball mill;

further, the primary grinding system comprises a first hoister, a V-shaped powder concentrator and a roller press which are sequentially connected end to end, and a large-particle material outlet of the V-shaped powder concentrator is connected with an inlet of the roller press;

10. The system for producing cement according to claim 9, characterized in that: the second-stage grinding system comprises a second lifting machine, a second finished product powder selecting machine and a ball mill which are sequentially connected end to end, a large-particle material outlet of the second finished product powder selecting machine is connected with the ball mill, and the second finished product powder selecting machine is communicated with the air distribution system;

and further, the fine particle material separator further comprises a main dust collector, a fine particle material outlet of the second finished product powder concentrator is connected with the main dust collector, and the main dust collector is connected with a main exhaust fan.